Treatment of sugar



United States Patent 3,522,092 TREATMENT OF SUGAR Beverly Cortis-Jones, 65 Peacock St., Seaforth, New South Wales, Australia No Drawing. Filed Oct. 23, 1967, Ser. No. 677,032 Claims priority, application Australia, Oct. 31, 1966, 13,299/66 Int. Cl. C13f 1/04; A23] 3/00 US. Cl. 127-63 4 Claims ABSTRACT OF THE DISCLOSURE The present invention has been developed to provide a method of retarding color development in raw sugar during conditions of prolonged storage.

It is well known that raw sugar is susceptible to color development during storage and that the rate of color development is accelerated very noticeably as the storage temperature rises. The greater part of the worlds supply of cane sugar is produced in tropical or near-tropical areas where high ambient temperatures are usual, and when raw sugar is stored in bulk in such areas the temperatures of the stored sugar may well remain at a high level for periods of several months. Under such conditions of storage, color development can eventually become severe.

It has now been found that certain non-toxic inhibitor agents can significantly retard color development in raw sugar when dispersed therein.

Broadly, the invention provides a method of retarding color development in stored raw sugar, comprising dispersing therein an inhibitor agent consisting of a magnesium oxy-compound selected from the group consisting of magnesium oxide, magnesium hydroxide and magnesium carbonate. As used hereinafter, the term inhibitor agent means a magnesium oxy-compound belonging to this group.

In the course of experiments leading to this invention, a great variety of other non-toxic materials were investigated with a view to determining their possible application in retarding color development in raw sugar. While a slight degree of inhibition was noted in a few of the investigated cases, such inhibition was found to be considerably less than the inhibition which is possible when using an inhibitor agent according to the invention. Example 4 hereinafter describes an experiment in which one such non-toxic material (magnesium chloride) is investigated and compared with an inhibitor agent according to the invention.

The development of color in raw sugar is attributable to the slow formation of colored compounds form impurities (such as reducing sugars and amino acids) which are concentrated in the syrup film adhering to the sugar crystals. Several different reaction sequences are known to contribute to this formation of colored compounds.

While the mechanism of inhibition according to the invention is complex, it appears that each of the inhibitor 3,522,092 Patented July 28, 1970 "ice agents interferes at least with (i) the known color forming reaction sequences involving the Maillard reaction, and with (ii) the known sequence of reactions contributing to the carmelisation of reducing sugars.

Evidence with regard to (i) has been obtained by an experiment using a model system in which a carrier of glass beads was first coated with a syrup comprising inter alia glucose (a reducing sugar) and glycine (an amino acid). Some samples of the coated beads were then treated with a quantity of powdered inhibitor agent, while others were not treated. After prolonged storage at an elevated temperature, it was noted that the degree of color development in the untreated samples far exceeded the degree of color development in the treated samples. Evidence with regard to (ii) has been obtained by a similar experiment using another model system in which refined sugar crystals were coated with a syrup comprising glucose and fructose.

Since the impurities responsible for color development in raw sugar occur predominantly in the syrup film, and since the total volume of syrup in a given batch of raw sugar is a very small fraction of the volume occupied by the sugar, it is not surprising that color development can be markedly inhibited by the use of relatively small concentrations of the selected inhibitor agent.

As will be illustrated in the examples hereinafter, it has been found that satisfactory color inhibition can be achieved under conditions of storage which are quite severe (as regards temperature and duration of storage) by using as little as 0.05 gram of the inhibitor agent per grams of raw sugar. Under less severe conditions, it has been found possible successfully to use the inhibitor agent at a concentration of 0.01% by weight.

When added in such small quantities as those mentioned, it will be appreciated that the subsequent removal of the inhibitor agent from the sugar presents no serious problem. I

The inhibitor agent can be added to the raw sugar in any convenient manner.

Magnesuim oxide, magnesium hydroxide and magnesium carbonate are each obtainable as a fine, light powder and can be added to the sugar in this form. With suitable mixing, the powder can be readily dispersed therein and, in spite of its insolubility, can thus be brought into effective contact with the compounds responsible for color development.

While this method of addition to the sugar is preferred (on grounds of convenience and economy), it will nonetheless be appreciated that the inhibitor agent can also be added thereto in other forms, for example in an aqueous slurry.

Examples 1 to 5 hereunder are on a laboratory scale, and in each case the following general method was employed:

A number of samples (each, 600 grams) were taken from a raw sugar of known purity and moisture content, and were separated into the categories experimental (one or more samples) and contro (one sample). The experimental samples were each mixed thoroughly (uniform conditions) with a known quantity of the selected powdered inhibitor agent or other additive; no addition was made to the control sample but this was nonetheless subjected to the same degree of mixing as the experimental samples. The experimental and control samples were introduced into identical glass jars, which were then sealed and stored in an incubator at the selected storage 3 temperature. At the same time, a measure was obtained of the pre-storage color density of the raw sugar, and this was subsequently compared with color density measurements of the ditferent samples after one or more storage periods had elapsed.

Example 6 hereunder is on a commercial scale, and the method used is described therein.

The color density of a sample of raw sugar can be measured in terms of the color density of its aqueous solution. In the case of the present examples, aqueous solutions of the same concentration were prepared weight/ volume in each of Examples 1 to 5; 50%, weight/ volume in Example 6). After filtering the solutions and adjusting the pH to the same value (usually 7), color densities were estimated by a conventional technique, using light with a wavelength of 420 miilimicrons. Referring to these solutions, the color units mentioned in Example 6 are calculated as:

1,000Xoptical density (420 m Solution concentration (g./ml.) Xcell length (0111.)

As used hereinafter in Examples 1 to 5 the term inhibition of color development (percent) relates to the fraction, color density difference between control and experimental samples to color density gain for control sample, expressed as a percentage.

EXAMPLE 1 In this case, the raw sugar was of approximately 98.5 I.S.S. (International Sugar Scale) and of 0.21% moisture content, and three experimental samples were used. The inhibitor agent was magnesium oxide, and this was incorporated in the experimental samples in respectively the following concentrations by weight: 0.01%, 0.03%, 0.05%. The storage temperature was 100 F. and color densities were measured after storage periods of (a) 107 days, (b) 158 days, (c) 342 days. Results are recorded in Table 1.

TAB LE 1 Inhibition of color development (percent) Magnesium oxide (percent) (a) EXAMPLE 2 The method of Example 1 was repeated in all respects except that storage was conducted at a temperature of 131 F. and color densities were measured after a single storage period of 37 days. Results are recorded in Table 2.

TABLE 2 Inhibition of color Magnesium oxide (percent): development (percent) EXAMPLE 3 EXAMPLE 4 In this case, the raw sugar was of approximately 97.8

1.5.8. and of 0.5% moisture content, and two experimental samples were used. An inhibitor agent of magnesium hydroxide was incorporated in one experimental sample, and an additive of magnesium chloride was incorporated in the other experimental sample. The concentrations of magnesium in both cases corresponded to an 0.04% concentration by weight of magnesium oxide.

The storage temperature was 131 F. and color densities were measured after a single storage period of 38 days. It was found that the inhibition of color develop ment in the sample containing magnesium hydroxide was 28%, while that in the sample containing magnesium chloride was zero.

EXAMPLE 5 In this case, the raw sugar was again of approximately 97.8 1.5.5. and of 0.5% moisture content, and two experimental samples were used. An inhibitor agent of magnesium oxide was incorporated in one experimental sample in 0.05% concentration by weight, and an inhibitor agent of magnesium carbonate was incorporated in the other experimental sample in 0.10% concentration (Le. the two inhibitor agents were used in approximately equimolar amounts).

The storage temperature was F. and color densities were measured after a single storage period of 263 days. It was found that the inhibition of color development in the sample containing magnesium oxide was 52%, and that in the sample containing magnesium carbonate was 32%.

EXAMPLE 6 A commercial batch of approximately 1,600 tons of raw sugar as separated from the centrifugals in a tropical cane sugar mill was treated with approximately 0.65 ton of magnesium oxide powder. The sugar was of approximately 97.90 1.8.8. and 0.5 moisture content. Intimate mixing of the inhibitor agent with the sugar was effected by the mechanical agitation occurring naturally in mill handling (e.g. in the conveyor and drier systems) and the final concentration by weight of magnesium oxide in the batch was 0.0350.045%. The sugar was then stored in a single heap for 26 weeks.

consecutively, a control commercial batch of approximately 1600 tons of raw sugar was separated from the centrifugals at the same tropical mill (the same production conditions) and was stored in a single heap for 26 weeks (no inhibitor agent added). This sugar was of approximately 97.70 1.8.8. and of approximately 0.5% moisture content.

Pre-storage and final color density determinations of both sugars were obtained in the manner already described. The pre-storage color densities of the treated sugar and control sugar were respectively 4230 and 3920 units; the color densities after storage were respectively 5105 and 6150 units.

I claim:

1. A method of retarding color development in raw sugar during conditions of prolonged storage, comprising dispersing therein concentration of not less than about 0.01% by weight of an inhibitor agent consisting a magnesium oxy-compound selected from the group consisting of magnesium oxide, magnesium hydroxide and magnesium carbonate.

2. The method according to claim 1, in which the inhibitor agent is dispersed in the raw sugar in the form of a powder.

3. The method according to claim 1, in which the inhibitor agent is powdered magnesium oxide, the concentration whereof is selected within the range of 0.01 to 0.05% by weight.

4. The method according to claim 1, in which the inhibitor agent is dispersed in the raw sugar in the form of an aqueous slurry.

(References on following page) References Cited UNITED STATES PATENTS Klopfer 12730 X Krister 12729 X 5 Sklar 127-46 Goodfriend 99-141 X Kooistra et a1 99-150 6 OTHER REFERENCES Ballester: Elguanite, an Emergency Juice Preservative, Sugar y Azucar, 54, No. 7, 17, 18 (1959).

MORRIS O. WOLK, Primary Examiner D. G. CONLIN, Assistant Examiner US. Cl. X.R. 

